1. Field of the Invention
The present invention relates generally to web printing presses and more particularly to a folder for a web printing press as well as to a method for cross-folding printed products.
2. Background Information
Web printing presses print a continuous web of material, such as paper. The continuous web then is cut in a cutting unit so as to form signatures which can then be folded in a folder or arranged in different manners, including providing a cross-fold. However, when variable length cut-off is desired, for example in order to decrease the signature length, it is often necessary to alter the tangential web velocity ratio between the folder and the printing units of the printing press. As a result, the velocity of the signature has to increase after it is cut from the web, which is counterproductive to downstream transport functions. Signatures thus often must be decelerated in a deceleration device. However, conventional fan/bucket deceleration devices often damage the signatures, e.g. through dog-earing, or jam the folder because the transfer from or to the deceleration device fails.
U.S. Pat. No. 5,865,082 discloses an apparatus for forming signatures from a web of material. A pair of rotating cylinders cuts the web to form signatures. A plurality of conveying elements traveling in two loops holds the web as the web passes between the cutting cylinders. The conveying elements thus also hold the signatures as they are formed. This device has the disadvantage that the cutting cylinders merely rotate so that the tangential web velocity ratio of the folder with respect to the printing units must be increased to decrease signature length. Moreover, no fold is provided to the signature.
Commonly-owned U.S. patent application Ser. No. 09/452,975 filed Dec. 2, 1999, which is not prior art to the present application and which is hereby incorporated by reference herein, discloses a variable-length cut-off folder and method. No folding of the printed products is addressed.
An object of the present invention is to provide a reliable device and method for cutting a web into signatures, while permitting for variable-length formats, and to provide a cross-fold to the resultant printed products.
The present invention provides a device for cutting a web of material into signatures and folding the signatures. The device includes a first set of movable elements and a second set of movable elements, the web moving between the first and second sets of movable elements. The first set of movable elements includes a first cutting element and a second cutting element variably-spacable with respect to the first cutting element, and the second set of movable elements includes a first gripping element for interacting with the first cutting element and a first tucking element variably-spacable with respect to the first gripping element.
The present device permits a web to run at a similar speed through the folders and the printing units, while still permitting variable length cut-offs and folding of the printed products.
In one embodiment of the present device, the first set of movable elements includes a first jaw element for interacting with the first tucking element. The jaw element, which preferably is spaced to provide a cross-fold in the middle of the signature, can then deliver the folded signature to a conveyor belt.
In a second embodiment of the present device, a rotating jaw cylinder is located adjacent the second set of movable elements after the signature formation area, the first tucking element interacting with jaws of the jaw cylinder.
The first set of movable elements preferably run in a first closed loop, the first closed loop having a signature formation area. The second set also preferably move in a second closed loop and interact with the first set of movable elements in the signature formation area.
The cutting elements may include either an anvil or blade. If the cutting element includes a blade, the interacting gripping elements include an anvil for the blade. If the cutting elements include an anvil, the gripping elements include a blade. The gripping elements also include a gripper for holding the signature in place.
The movable elements may be driven along a track at variable spacing using controlled disks or variable motor technology as disclosed in U.S. patent application Ser. No. 09/452,975 incorporated by reference above. The blade and anvil and gripping devices may also be similar to those disclosed in the ""975 application.
The present invention also provides a method for cutting a web into signatures and folding the signatures comprising the steps of:
spacing a plurality of cutting elements along a first side of the web to set a signature length;
spacing a plurality of gripping elements on a second side of the web opposite the plurality of cutting elements, the web traveling between the cutting elements and the gripping elements in a signature formation area; and
spacing a plurality of tucking elements on the second side of the web, one of the tucking elements being spaced in between two of the plurality of gripping elements.
Preferably, the plurality of tucking elements and the plurality of gripping elements are alternately spaced.
The method may include spacing at least one jaw element on the first side of the web opposite the plurality of tucking elements in the signature formation area. Alternately, the method may include gripping a signature at a cross-fold with a jaw cylinder located opposite the plurality of tucking elements.